人工降雨對不飽和土壤夯實邊坡入滲行為之研究

Infiltration Behavior of Unsaturated Compacted Soil Slopes Subjected to Artificial Rainfall

黃立杰(Li-Jie Huang)

指導教授 ： 楊樹榮

國立屏東科技大學/工學院/土木工程系所/碩士(2014年)

https://doi.org/10.6346/NPUST.2014.00301

摘要

臺灣每逢颱風豪雨，夯實土壤邊坡崩塌事件頻傳，原因眾多，其中有可能因土壤邊坡夯實時夯實度不足，或是夯實初始含水量控制不佳等因素，造成降雨入滲後邊坡破壞。本研究於實驗室針對不飽和夯實邊坡進行人工模擬降雨試驗，探討不同夯實度、不同初始含水量與不同降雨強度作用下對邊坡降雨入滲行為之影響。試驗中於邊坡土體內部埋設土壤水份計與張力計，用以監測降雨入滲後土體內部含水量與基質吸力變化情形。本研究探討不同入滲深度下之降雨歷時與基質吸力之時間因子之關聯性。
試驗結果顯示隨著夯實度下降，邊坡降雨入滲率大，誘發基質吸力下降時間點提早發生，且吸力快速下降，導致邊坡破壞規模相較於高夯實度來的大。另一方面，夯實初始含水量的增加會使土壤結構改變，導致雨水入滲邊坡時間延長，誘發基質吸力下降時間點延遲，吸力下降趨緩，而有助於邊坡之穩定性。
此外，當降雨強度大於土壤邊坡之滲透係數時，雨水在邊坡表面產生逕流現象，促使破壞方式為表面沖蝕與粒料流失，且隨著降雨強度提高，邊坡表面逕流大使邊坡破壞區域擴大，然而降雨度對入滲行為並未產生影響。

關鍵字

不飽和土壤夯實邊坡 ； 入滲行為 ； 基質吸力

並列摘要

In Taiwan, landslides on compacted slopes easily occur due to heavy rains brought by typhoons. This may be attributed to inadequate compaction degree or poorly controlled initial moisture content. Under these circumstances, slope failure occurs after rainfall seepage. Therefore, artificial rainfall simulation experiments were carried out in the laboratory to discuss the effects of different degree of compaction, initial compaction moisture content and the rainfall intensity in unsaturated compacted soil slopes subjected to rainfall. During these tests, the soil moisture and suction meters were buried into the soil to monitor the variation of moisture content and matric suction. In this study, the relationship between rainfall duration and the time factors of matric suction was discussed under different infiltration depth.
The results show that the lower degree of compaction together with the larger porosity makes infiltration rate higher, the saturation time of rainwater infiltrating slope faster, and the drop time of matric suction rapider. Besides, in consequence of fast descending slope of suction, the destructive scale is greater than that at the high degree of compaction. On the other hand, with increase in initial moisture content, the soil structure transforms. Extending time of rainwater infiltration induces the delay of decline in matric suction time and slows down suction slope, which facilitates the stability of the slope.
In addition, when the rainfall intensity is greater than the permeability of soil, rainwater dropping on the surface of the slope results in the runoff, prompting the destructions such as the surface erosion and the loss of pellets. That is because when it rains heavily, the surface of runoff becomes greater, which consequently enlarges the destruction area of slopes.

並列關鍵字

Unsaturated soil compaction slope ； Infiltration behavior ； Matric suction

參考文獻

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